Wind farms comprise pluralities of wind energy installations, wherein the power generated in the wind energy installations is first fed into a grid internal to the wind farm. At a transfer station the power from the grid internal to the wind farm is fed to an external supply grid. The grid internal to the wind farm is usually a medium-voltage grid, whereas the external supply grid is a high-voltage grid. A transformer is therefore provided at the transfer station to transform between the voltage of the medium-voltage grid and the voltage of the high-voltage grid. Offshore wind farms are usually connected to the supply grid by a single power cable, where the transfer station and, when relevant, the transformer, are arranged on a central platform of the wind farm.
A supply of power is necessary for the operation of individual wind energy installations or of a wind farm, so that particular electrical components of the wind energy installations or of the wind farm can be operated. These electrical components include, amongst other things, control units, drive units for the adjustment of pitch and/or azimuth, and for the obstruction lighting. This energy supply is usually ensured by the supply grid. If the supply of energy from the supply grid breaks down, the operation of the electrical components can also no longer be ensured. Components such as the obstruction lighting that are necessary for the survival and/or safety of the wind energy installations are also affected by this.
The supply of energy breaks down, for example, if the supply grid fails, or if there is a fault in the power cable or damage to the transfer station. The latter cases are particularly critical for offshore wind farms, since some of these are only connected to the supply grid over a single power cable and a single transfer station, whose repair is time-consuming and, in some cases, can take several months.
The provision of an independent power supply (UPS) at each wind energy installation, with which individual consumers of the wind energy installations can still continue to be operated when the supply of energy over the supply grid fails, is known from the prior art. UPSs according to the prior art have a limited capacity, and can, for instance, supply the electrical components of a wind energy installation with energy for 24 hours. A longer failure of the supply of energy over the supply grid requires the UPSs to be charged regularly.
The provision of a central emergency power generator at the transfer station for charging the UPSs is known. The charging of the UPSs can be carried out here for all of the wind energy installations at the same time, or only for some of them. The emergency power generator must, whatever the case, be dimensioned such that at no stage is all the energy stored in the UPSs of the individual wind energy installations completely used up, the electrical components of the wind energy installations then no longer being capable of operation.
A commercial fuel-powered generator arranged at the transfer station of the wind farm is usually employed as an emergency power generator. In offshore wind farms in particular, the space available for such a generator and its fuel tank (which can, for instance, be arranged on a central platform of the wind farm) is limited, for which reason the fuel tank is often small. This has the consequence that frequent refueling is necessary and this, as a result of the distance and the weather, is difficult with offshore installations.